If you are going to finance the car why not go to a reputable dealer, the car will be checked, many of them have a 3-5 day satisfaction clause now, bring the car back if you dont like it, they will make sure it passes emissions,

i have bought many both ways, the truck i replaced my diesel with was at phil long, was great deal, way cheaper than private sales on this particular truck it is a very rare package, they repaired a couple items for free cause they were safety items, gave me two years free oil changes even on a used car, 3 days to return it if i did not like the deal.